1. Field of the Invention
The present invention relates to high and very high voltage electric lines, for instance the most modern 1000 KV lines, and more specifically, to a system for the suspension of the conductors of said lines.
It is known that, in the lines of this type, conductors in a bundle are normally used, each bundle comprising a given number of sub-conductors--for instance six, eight, ten or even twelve sub-conductors--distributed over a circumference having a diameter of, for example, 900 to 1250 mm.
On account of the weight and size of such bundles of conductors, quite important problems have to be faced in connection with the system for the suspension thereof to the poles or standards of the line.
It should also be noted that, for lines of this type, use is preferably made--for each suspension point of the line--of a pair of struts, hinged at the base and connected at the top by an insulating chain or catenary, to which the conductors are hooked, said struts being also kept in position by tie rods or stays, anchored to the top of the poles and onto the the ground and mounted in opposition to the tractive force of the catenary.
2. Description of the Prior Art
According to one of the known techniques, diagrammatically illustrated in FIGS. 1 and 2, a catenary 4 of mutual connection is arranged between the poles or standards 1, which are hinged onto the ground in 2 and kept in position by tie rods or stays 3. Said catenary has a broken-line course, determined by the fact that the conductors are hooked thereto in correspondence of the corner points. The straight sections of said catenary are constituted by one or more insulating catenaries, series and/or parallel connected, while a suitably configured suspension yoke 5 is provided in correspondence of each corner.
A yoke 5 is shown in FIG. 2 as having an asymmetric configuration, deriving from the fact that it is one of the yokes in a lateral position. The yoke provided in the central position obviously has a symmetrical configuration. In any case, to each yoke--which practically forms an element of the catenary--is suspended the true and proper support of the bundle of conductors.
According to one of the previously carried out embodiments, such a support is constituted by a pair of rods 6 hanging onto the yoke 5, rigidly mounted at a predetermined mutual distance and carrying in turn brackets 7, to which the single sub-conductors of the bundle are directly connected. The configuration of the brackets 7 and their positioning along the rods 6 are such that the suspension points of the single sub-conductors get to find themselves uniformly distributed over a circumference 8.
The main faults of such a suspension support lie in:
its general configuration, which is very bulky and has a very low barycenter in respect to the suspension point of the insulating catenary, which makes the whole system easily subject to the oscillations caused by the wind, or to high bankings in the corner positions of the line;
the scarce protection against glow discharge, which compels to provide for supplementary protection systems, between the insulating catenaries and the bundles of sub-conductors, against the electric glow discharge deriving from the very high voltage of the line;
the requirement, also in relation to what has just been said, of realizing various types of supports, differing one from the other, in order to adapt oneself to different points of connection and to the different positions which they take up along the line;
and, finally, the presence of single connection points, for instance in correspondence of the yoke 5 or of the rods 6, the accidental breaking of which could easily lead to a complete or partial collapse of the line.